The two would send correspondence to each other as if they were the main characters.

During his month in jail, Brown was allowed to send and receive correspondence.

E-mail allows You to send correspondence anywhere in the world.

You will find the telephone number on the correspondence sent to you.

You'll find the contact details you need on the correspondence sent to you.

"In fact there were several others to whom you sent such correspondence, weren't there?"

"Even though you didn't send the stuff, that correspondence could be used against you."

Include any supporting documents or correspondence that may further explain the situation, but do not sent originals.

It is important that all correspondence sent to this address is dealt with promptly.

Thus began what Bishop calls "the first ever transatlantic science fiction collaboration", with all correspondence sent by post.